netfilter: nf_dup4: Unmask upper DSCP bits in nf_dup_ipv4_route()

Unmask the upper DSCP bits when calling ip_route_output_key() so that in
the future it could perform the FIB lookup according to the full DSCP
value.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/nf_dup_ipv4.c

@@ -15,6 +15,7 @@
 #include <net/icmp.h>
 #include <net/ip.h>
 #include <net/route.h>
+#include <net/inet_dscp.h>
 #include <net/netfilter/ipv4/nf_dup_ipv4.h>
 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 #include <net/netfilter/nf_conntrack.h>
@@ -32,7 +33,7 @@ static bool nf_dup_ipv4_route(struct net *net, struct sk_buff *skb,
 		fl4.flowi4_oif = oif;
 
 	fl4.daddr = gw->s_addr;
-	fl4.flowi4_tos = RT_TOS(iph->tos);
+	fl4.flowi4_tos = iph->tos & INET_DSCP_MASK;
 	fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
 	fl4.flowi4_flags = FLOWI_FLAG_KNOWN_NH;
 	rt = ip_route_output_key(net, &fl4);